What is Acid Rain?

Although the term acid rain was coined in the early 1850s, around the time of the Industrial Revolution, it didn't become a rallying cry for environmental reform until the late 1960s. The devastating effects of this precipitation on the world's water supply, fish populations, and plant life can be traced back scientifically to the use of fossil fuels in factories. Public demonstrations held in the early 1970s helped bring about major changes in pollution and emission standards. Although the problem still exists worldwide, many companies have taken steps to minimize its root causes.

Acid rain is precipitation that contains traces of pollutants, primarily sulfur dioxide and nitrogen oxide gases created as fossil fuels like coal or oil burn. Around the time of the Industrial Revolution, large factories began to use coal to power their machinery. As the coal burned, it released large amounts of sulfur and nitrogen gases into the air through smokestack exhaust. These gases would often reach the upper levels of the atmosphere and drift into areas where natural rainclouds regularly formed.

Particles of these highly acidic sulfur and nitrogen gases bond with the natural rain and fall to the ground during storms. Natural rainfall should have a pH level around 5.6, which is mildly acidic but not considered harmful. When sulfur dioxide and nitrogen oxide mixes with this rainwater, the pH level can quickly drop below 5.0. In certain areas located near large factories, the level occasionally approaches the acidity of pure vinegar. This is acid rain.

Acid rain does not always occur in the same area as the pollutants that cause it. Once the acidic pollutants leave the smokestack, they are caught up in the natural jet streams and weather fronts of the atmosphere. The sulfur and nitrogen gases might travel for a great distance before encountering rain-producing clouds.

In many cases, this precipitation is often more of a problem for neighboring countries than for those with the pollution-causing factories. Canada, for example, suffers effects of pollutants produced by factories located in New York and New Jersey. Scandinavian countries are plagued by acid rain originating from Russia and China.

The negative effects of acid rain can be seen everywhere. It can kill grasses and other protective ground cover, leading to more incidence of erosion and acidic soil levels. The precipitation can strip away the waxy coating on leaves, leaving trees more vulnerable to fungal damage and dehydration. Fish cannot survive or breed in water with a pH value below 5, which means that this pollution can kill off an entire population of fish.

It can also cause damage to exposed metal and concrete supports, grave markers and historical monuments, and damaged structures can be very costly to repair.

Following the stricter guidelines imposed by the Environmental Protection Agency (EPA), many factories in the United States have voluntarily installed special scrubbers to filter their emissions. These scrubbers use limestone and other basic chemicals to attract the sulfur particles before they leave the smokestack. In some cases, the resulting compound is sold to other companies as a form of gypsum, which is used to create drywall panels. Some nitrogen oxide still reaches the atmosphere, but it doesn't affect the pH level of rainfall as much as the sulfur dioxide once did.